The present invention relates to a magnetic recording playback device, such as a hard disk drive, and, more particularly, to a mechanism which can easily change the error correction capability according to the situation.
In a conventional magnetic recording playback device, an error correcting code which satisfies a target error rate has been developed, at the developmental stage of the device, in consideration of the playback output of an MR (magneto-resistive effect element) head, the SNR (input/output noise ratio), the defect conditions of mediums, and the like.
As an error correction code generally used in the magnetic recording playback device, there is a Reed-Solomon code (hereinafter, referred to as RS code). This is a method of representing a data sequence to be recorded by utilizing an element of a Galois field at a certain level, performing a division by employing a generating polynomial, and adding the remainder of the division, as redundant bytes, to the end of data to be transmitted. When the correction capability is enhanced, the redundant bytes increase as a tradeoff. Further, when a strong error correcting code is added to a massive data sequence, the arithmetic processing for encoding/decoding becomes complicated, thereby arising a problem of correction processing rate.
Accordingly, there has generally been utilized an interleaving configuration in which a massive data sequence is divided into plural blocks, and redundant bytes that satisfy a target error rate are added to each block. For example, for one sector (512 bytes) of a hard disk, redundant bytes having the capability of correcting several bytes (2n bytes in the case of n-fold correction) are added to data, and the data having a predetermined size (512+2n bytes) is transmitted. However, as the recording density is increased, the redundant bytes tend to be larger to maintain the error rate and, therefore, the redundant bytes would be a factor which further increases overhead of the drive (load on the system).
The conventional magnetic recording playback device is constituted as described above, and redundant bytes that satisfy a target error rate are uniformly added to data in predetermined block units. However, the same amount of redundant bytes are added to all of the data blocks when coding is carried out, regardless of the condition of tracks on which data are to be recorded or the electric characteristics of a write head and an MR head, and therefore, the redundant bytes cause an undesirable tendency toward an increase in overhead of the drive.
The present invention is made in view of the above-described problems and has for its object to provide a magnetic recording playback device which can reduce overhead of a drive due to redundant bytes, while maintaining a target error rate.
A magnetic recording playback device according to a first aspect of the present invention comprises a recording magnetic head for recording or deleting data on/from a magnetic record medium; a playback magnetic head for reproducing the recorded data; a parameter acquiring means for acquiring plural parameters relating to the operating characteristic of the recording medium and the operating characteristics of the respective magnetic heads, when the respective magnetic heads perform writing/reading operations; a redundant data adding means for adding redundant data having a predetermined number of bytes to data before being written in the recording medium; a data encoding means for encoding the data to which the redundant data is added; an error correction capability value storage means which holds plural error correction capability values each corresponding to a combination of the parameter relating to the operating characteristic of the recording medium and the parameters relating to the operating characteristics of the respective magnetic heads; and a control means for selecting an error correction capability value corresponding to the parameters acquired by the parameter acquiring means from the error correction capability values stored in the error correction capability storing means, and controlling the redundant data adding means so that it adds redundant data having a predetermined number of bytes according to the selected error correction capability value to the data to be recorded.
According to a second aspect of the present invention, the magnetic recording playback device defined in the first aspect further comprises a decoding means for selecting an error correction capability value corresponding to the parameters acquired by the parameter acquiring means from the error correction capability values stored in the error correction capability storing means, and performing decoding on the basis of the selected error correction capability value when reproducing the data to which the redundant data having a predetermined number of bytes are added.
According to a third aspect of the present invention, in the magnetic recording playback device defined in the first aspect, when the error correction frequency at data reproduction deviates from a predetermined value, the control means changes the error correction capability values stored in the error correction capability value storing means in accordance with the change in the error correction frequency at data reproduction.
As described above, the magnetic recording playback device according to the first aspect of the present invention comprises a recording magnetic head for recording or deleting data on/from a magnetic record medium; a playback magnetic head for reproducing the recorded data; a parameter acquiring means for acquiring plural parameters relating to the operating characteristic of the recording medium and the operating characteristics of the respective magnetic heads when the respective magnetic heads perform writing/reading operations; a redundant data adding means for adding redundant data having a predetermined number of bytes to data before being written in the recording medium; a data encoding means for encoding the data to which the redundant data is added; an error correction capability value storage means which holds plural error correction capability values each corresponding to a combination of the parameter relating to the operating characteristic of the recording medium and the parameters relating to the operating characteristics of the respective magnetic heads; and a control means for selecting an error correction capability value corresponding to the parameters acquired by the parameter acquiring means from the error correction capability values stored in the error correction capability storing means, and controlling the redundant data adding means so that it adds redundant data having a predetermined number of bytes according to the selected error correction capability value to the data to be recorded; and the number bytes is varied according to the situation in such a manner that low-level redundant bytes are added to a region where the error frequency is low while high-level redundant bytes are added to a region where the error frequency is high. Therefore, the number of redundant bytes can be variable, whereby reduction in overhead of the magnetic recording playback device can be achieved easily.
Furthermore, according to the second aspect of the present invention, the magnetic recording playback device defined in the first aspect further comprises a decoding means for selecting an error correction capability value corresponding to the parameters acquired by the parameter acquiring means from the error correction capability values stored in the error correction capability storing means, and performing decoding on the basis of the selected error correction capability value when reproducing the data to which the redundant data having a predetermined number of bytes are added. Therefore, the data to which the redundant bytes are effectively added can be decoded with efficiency.
Furthermore, according to the third aspect of the present invention, in the magnetic recording playback device defined in the first aspect, when the error correction frequency at data reproduction deviates from a predetermined value, the control means changes the error correction capability values stored in the error correction capability value storing means in accordance with the change in the error correction frequency at data reproduction. Therefore, even when the use environment changes by aging or the like, the error correcting efficiency can be maintained in accordance with the change, whereby a highly reliable device can be provided.